Giant magnetoresistance in sputtered magnetic superlattices (invited) (abstract)

Abstract

Recently, large values of saturation magnetoresistance (SMR) were reported in single-crystal Fe/Cr superlattice structures prepared by molecular-beam- epitaxy (MBE) techniques.1 We have prepared similar polycrystalline superlattice structures by dc magnetron sputtering in a high-vacuum deposition system and find comparably high SMR values of up to 50% for Cr-layer thicknesses of ≅8 Å. Magnetization-versus-field data suggest that successive Fe layers are coupled antiferromagnetically with one another, as for the MBE-grown films. Magnetic fields of up to 20 kOe are required to align Fe layers 20 Å thick, implying substantial exchange-coupling energies between the Fe layers. While the magnetization curves have a weak temperature dependence even for temperatures above the Néel temperature of bulk Cr, the SMR decreases as the temperature is increased. Work on related structures which do and do not show giant SMR effects will be discussed.